Prevention of incompatible keyboard selections from being entered during power initialization

ABSTRACT

A control system for an apparatus wherein a keyboard for user selection has a plurality of first lines and a plurality of second lines coupled to a programmable microprocessor. The keyboard includes a plurality of switch elements arranged to selectively connect a particular one of the plurality of first lines to a particular one of the set of second lines. The control system is disabled while powering-up so that incompatible keyboard selections cannot be entered by the user.

CLAIM OF PRIORITY

[0001] Priority is claimed from U.S. provisional patent application No.60/208,754 filed Jun. 2, 2000.

FIELD OF THE INVENTION

[0002] The present invention relates to apparatus which have a keyboardfor inputting information/commands to the device, and more particularly,to the prevention of a user from inputting incompatibleinformation/commands during power-up of the apparatus.

BACKGROUND

[0003] Scanned matrix keyboards are almost universally employed incontrol system which include microcontrollers, due to the efficiency ofscanned matrix keyboards in minimizing the number of wire connectionsrequired. In a scanned matrix keyboard, a set of drive lines and a setof sense lines are logically organized as rows and columns, and each ofa plurality of individual key switches is electrically positioned at theintersection between a particular drive line and a particular sense lineto electrically and logically connect a particular sense line to aparticular drive line to define a matrix intersection point when theswitch is actuated by a user.

[0004] Thus a coding pattern is established from an encoding setincluding connection of a sense line to at least a particular one of theset of drive lines according to the programming of the microprocessor.Conventional practice is to periodically scan the keyboard, e.g., bymomentarily applying a bias or signal to each of the drive lines insequence, while monitoring all of the sense lines in synchronism withthe activation of the drive lines, and thereby determining whichparticular key is being actuated.

[0005] With television receivers/players, e.g., color televisionreceiver, VCR, DVD players, if a user by chance happens to press aparticular combination of keyboard keys while powering-up the device,the receiver may switch into an undesirable service mode, which isintended to be used only during factory production set-up procedures.Once the television receiver is switched into such a service mode, theuser is very confused, and is unable to use the keys to switch out fromthe service mode, i.e., the user does not know that he/she mustdisconnect the AC power cord from the AC power, and should wait untilcapacitors within the television receiver discharge before re-insertingthe AC plug. It is desirable to avoid this situation from occurring.

SUMMARY OF THE INVENTION

[0006] A control system for an apparatus wherein a keyboard forinformation or command input has a plurality of drive lines and aplurality of sense lines coupled to a programmable microprocessor. Thekeyboard includes a plurality of switch elements arranged to selectivelyconnect a particular one of the plurality of drive lines to a particularone of the set of sense lines. The programming of the microprocessordisables the control system during power-up to prevent incompatible userinput during initialization.

BRIEF DESCRIPTION OF THE DRAWINGS

[0007] Referring now to the drawings wherein:

[0008]FIG. 1 is a schematic representation of a prior art keyboard witha microprocessor.

[0009]FIG. 2 is a partial schematic representation according to aspectsof the present invention.

[0010]FIG. 3 is a flow chart of the microprocessor programming and ofthe operation of FIG. 2.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT(S)

[0011]FIG. 1 shows an exemplary prior art keyboard arrangement whereinkeyboard 120 includes, for example, sixteen keys, and has four drivelines coupled to controller 110 at ports D0-D3, and four sense linescoupled to controller 110 at ports S0 through S3. Microcomputer 110includes a central processing unit (CPU) 112, a read only program memory(ROM) 114, and a random-access memory (RAM) 116. ROM 114 can be eitherinternal or external to microprocessor 110, and can containpreprogrammed control codes. Pull-down resistors 122 can be internal (asshown here) of microprocessor 110 or external (not shown), or pull-upresistors can be used. Such resistors assure that a line goes to onestate to another when no button is pressed, and thus assures that aknown result is achieved with the pressing of a key/button.

[0012] In operation keyboard 120 is scanned by microprocessor 110 whichsets bidirectional I/O ports (i.e., sense lines) S0 through S3 to theinput mode, and in turn, applies sequential high level signals to drivelines D0 through D3 in an output mode. Thus, drive lines D0 through D3produce a logic level 1 output. After the high level signal is movedfrom one drive line to another, each of sense lines S0 through S3 isread to see if a high level signal is present. Controller 110 candetermine which key is pressed because each key affects a unique driveline/sense line pair.

[0013] Referring now to FIG. 2, scanned keyboard drive line 210 innormal operation is a general purpose input/output (GPIO) configurationused to distinguish between switches connected to the keyboard senseinputs. However, the keyboard drive line herein also serves a dualpurpose. If keyboard drive line 210 is driven “high” duringinitialization, i.e., by the user depressing an appropriate key 214 onthe keyboard connecting a respective pull-up resistor 212 to drive line210, operational microprocessor 110 is programmed to enter a specialtest mode which is reserved for use during factory testing here thedrive line is externally driven “high” by a test fixture using anexternal voltage source.

[0014] To prevent the apparatus from entering this special testing modedue to keyboard input, operational microprocessor 110, by virtue of itsprogramming, reconfigures the keyboard sense lines as output linesrather than input lines, and sets them to a low state before readingdrive line 210. To test for the special test mode enable, the drive lineis made an input terminal of microprocessor 110. With the sense lines216 being driven low and sinking most of the current from respectivepull-up resistors 212, the pressing of a key 214 will not cause thesoftware to enter the special test mode, i.e., drive line 210 will notbe driven “high”. Thus, when sense lines 216 are programmed to be low,the keyboard is disabled, and when a key is pressed during power-up, thekeyboard will not work while initialization is in process. In this way,drive line 210 cannot be driven “high” by use of the keyboard, but onlyby the external voltage source. Once drive line 210 has been read duringpower-up, and it is not “high”, operational microprocessor 110 executesits programming, and makes sense lines 216 input terminals and makes thedrive line(s) output terminals once again for normal functioning, i.e.,a scanned keyboard as discussed above.

[0015] It should be noted that the present invention is equallyapplicable if logic levels are reversed, i.e., pull-up resistors arechanged to pull-down resistors and a low level is required to enable thedual function for drive line 210. In that case normally, sense lines 216would be driven low with the pressing of a key, and the drive line wouldbe short circuited to ground by the test fixture, i.e., the externalvoltage source is zero volts.

[0016] The exemplary embodiment shows one drive line. If there aremultiple drive lines, the other drive lines might also be set to be lowduring testing whether to enter the service mode even if only one of thedrive lines is being monitored to determine whether to enter the servicemode. Otherwise, multiple keys, simultaneously pressed, could causeanother drive line to go high. For example in FIG. 1, if D0 is set high,pressing keys 0 and 8 could cause drive D1 to read high. Of course, ifsome drive lines are not coupled to the microprocessor, then theirsetting upon initiation is not relevant to the present problem unless amultiple key press can cause the problem discussed immediately above.

[0017] Additionally, for the purposes of the present invention, the setof drive lines can be considered to be interchangeable with the set ofsense lines. The designation of an input line as a drive line or a senseline is just a matter of labeling.

[0018] Microprocessor 110 of the exemplary embodiment is an ST92196 madeby the STMicroelectronics Co., formerly SGS Thomson Inc. An extensivedata sheet is available from the manufacturer.

[0019]FIG. 3 shows a flow chart of the execution of the programming ofmicroprocessor 110 and the operation of FIG. 2, according to aspects ofthe present invention. The set is AC plugged-in for receiving power at310, the keyboard sense lines are made outputs at 312, the keyboardsense lines are driven low at 314, keyboard drive line is made an inputat 316, and the keyboard drive line is read at 318. A decision is madeat 320 depending upon whether the drive line is high, if yes, then thetest mode is entered at 322, and if no, the keyboard drive line is madean output at 324, keyboard sense lines are made normal inputs at 326,and normal operation is begun at 328.

[0020] As used herein, the terms power-up, start-up, or initializationare interchangeable, and mean when the device is turned “on” after anapplication of newly provided AC power, such as when the apparatus isnewly installed and the AC power supply is first switched “on”, or afterthe AC power has been shut off by, e.g., pulling the AC plug, a trippedcircuit breaker, a blown fuse, a power outage, etc. In such instances,the operational microprocessor executes its programming and disables thekeyboard during initialization, as disclosed herein. Additionally, asused herein, the terms unwanted, undesirable, and incompatible areinterchangeable.

1. A control system for an apparatus comprising: a keyboard having aplurality of first lines and a plurality of second lines coupled to aprogrammable microprocessor; the keyboard including a plurality ofswitch elements arranged to selectively connect a particular one of theplurality of first lines to a particular one of the set of second lines;the control system being disabled during powering-up of the apparatus bythe programming of the microprocessor.
 2. A control system comprising: akeyboard for user selection and having a plurality of first lines and aplurality of second lines coupled to a programmable microprocessor; thekeyboard including a plurality of switch elements arranged toselectively and electrically connect a particular one of the pluralityof first lines to a particular one of the set of second lines; at leastone switch element providing a selection during powering-up which isincompatible with other user selections; the control system beingdisabled during powering-up so that the incompatible keyboard selectioncannot be entered by the user.
 3. The control system of claims 1 or 2wherein the disabling of the control system during power-up isaccomplished by the microprocessor being programmed to make the firstlines and second lines output lines from the microprocessor duringpower-up.
 4. The control system of claim 3 wherein one of the firstlines and second lines are changed to be input lines for normal userinput after power-up.
 5. The control system of claim 3 wherein theincompatible keyboard selection can be forced upon the control systemduring power-up by externally overriding the microprocessor programming.6. The control system of claim 5 wherein the means for overriding themicroprocessor programming comprises a source of voltage applied to atleast one of the first lines and the second lines.
 7. A control systemcomprising: a keyboard for user selection and having a plurality offirst lines and a plurality of second lines coupled to respectiveterminals of a programmable microprocessor; the keyboard including aplurality of switch elements, at least one switch element arranged toselectively connect a particular one of the plurality of first lines toa particular one of the set of second lines; the control system beingdisabled while powering-up so that incompatible keyboard selectionscannot be entered by the user because the microprocessor is programmedto configure one of the first lines and the second lines to be outputlines during power-up.
 8. A control system comprising: a keyboard havinga plurality of first lines and a plurality of second lines coupled torespective terminals of a programmable microprocessor; the keyboardincluding a plurality of switch elements, at least one switch elementarranged to selectively connect a particular one of the plurality offirst lines to a particular one of the set of second lines; one of thefirst lines and the second lines being configured as output lines duringpower-up and configured as input lines after power-up.